New vaccine shows promise against H5N1 influenza

HCWs would be prime candidates for shot

A new vaccine against H5N1 avian influenza appears to be safe and effective, according to early research results. And health care workers may be among the first candidates for the vaccine, experts say.

With serum testing completed on about a third of the 450 vaccine subjects, "those results do suggest that the vaccine effectively induced antibody against the H5 influenza virus that would be expected to protect against the H5 flu," says John Treanor, MD, a professor of medicine at the University of Rochester (NY) and lead investigator for the avian influenza H5 vaccine study.

Higher doses of the vaccine are required compared to the annual influenza vaccine to produce the immune response, he says. However, the safety profile of the vaccine is identical, Treanor adds.

"It looks like we're headed down the right pathway, that we've got something that works. We will have a more precise estimate of exactly how frequently people will respond to the vaccine when more serum is tested."

The tests should be completed by the end of October, he says. Researchers then will expand the study to include the elderly and children.

Researchers also will be looking into dose-sparing alternatives that could enhance the vaccine, such as adjuvants and intradermal administration, Treanor says.

An H5N1 vaccine could be an important tool in the arsenal against avian influenza, but supply will be an issue. Recent shortages of influenza vaccine demonstrate the fragility of the manufacturing system, experts say.

Michael Osterholm, PhD, MPH, director of the Center for Infectious Disease Research and Policy at the University of Minnesota in Minneapolis, estimates that about 88 million to 100 million doses could be produced in the six months after pandemic influenza emerges.

"If you can only provide enough vaccine to protect 88 million to 100 million people [globally] in the first six months after the pandemic hits, that's a drop in the bucket," he says.

If vaccine production is diverted to make H5N1 vaccine for stockpiling, that would reduce the availability of the annual flu vaccine, Osterholm explains.

And the vaccine might not be a perfect match with the strain that circulates during an actual pandemic, Treanor acknowledges.

But experts do agree on one point. Increasing annual, interpandemic flu vaccination — including among health care workers — would mean increasing the manufacturing capability.

"A key message is to make sure that hospitals revisit their current influenza immunization programs and make sure that hospital employees who have patient care responsibilities do get annual immunizations," says Frederick Hayden, MD, professor of internal medicine at the University of Virginia Health Sciences Center in Charlottesville. "Increasing vaccination use during the interpandemic period will eventually allow for greater vaccine availability and acceptance.

"It's not just pandemic flu that we need to think about," he adds. "We need to think about the annual outbreaks as well."